The present disclosure relates to a solid-bowl screw centrifuge including a drum rotatable about, for example, a horizontal axis of rotation. A rotatable screw is arranged in the drum. The centrifuge includes a continuous solid discharge at one end of the drum and a continuous liquids discharge at an opposite end of the drum. Further included is at least one discontinuously acting outlet opening having a closure device.
A wide range of designs of solid-bowl screw centrifuges are known. As the drum slows down, the ring of liquid in the drum collapses below a threshold rotational speed, so that the residual liquid collects in the bottom of the drum. To allow the residual liquid that then remains to be completely emptied, or to prevent emptying via the solids side or the liquid side, it is known for the residual liquid to be discharged through separate outlet openings. Valves or slides are fitted into the separate outlet openings and may, for example, be spring-loaded, according to the document DE 41 30 759 A1.
Further prior art includes DE 36 209 12, which proposes that the liquid discharge be realized purely by openings in the drum lateral surface, which are assigned conical adjustment elements that can each be actuated by means of separate piston-cylinder units or slides. DE 39 11 320 A1 discloses a further prior art design.
The designs which have been described above are relatively complex and are susceptible to operational disruption. The present disclosure relates to a centrifuge of a more simple design than described above.
The present disclosure relates to a solid-bowl centrifuge that includes a drum rotatable about a horizontal axis of rotation, a screw arranged in the drum, a continuous solids discharge located at a first end of the drum, and a continuous liquid discharge located at a second, opposite end of the drum. Further included is at least one discontinuously acting outlet opening including a closure device, the closure device including a ring configured to be axially displaced relative to the horizontal axis of rotation and rotatable with the drum during an operation of the centrifuge. Also included is an actuating device assigned to the closure device, by which actuating device the ring is displaced into a first position which opens the at least one outlet opening and into a second position which closes the at least one outlet opening.
According to the present disclosure, the at least one outlet opening is assigned a ring. The ring can be axially displaced relative to the drum axis and rotates with the drum in operation. The ring is assigned an actuating device, by which actuating device the ring can be displaced into a position which opens up the at least one outlet opening and into a position which closes the at least one opening completely. This design is of simple construction and is operationally reliable, since it does not use valves or individual slides, which are susceptible to faults.
Moreover, the centrifuge according to the present disclosure allows simultaneous opening and closing of all emptying or outlet openings using just one master actuating device. For CIP (Cleaning In Process) applications, there is no need for the drum to be stopped first, since the CIP program can be initiated immediately after emptying, with the drum still rotating or even without any reduction in speed at all.
When the drum is stopped, undesirable residual emptying, in particular toward the solids side, is avoided in a simple way. The liquid level collapses as a result of an increasing drop in speed. By contrast, in the prior art, under certain circumstances liquid was washed over through the drum outlets. Liquid oscillations as the drum stops are also avoided.
Further prior art includes DE 102 09 025 A1. FIG. 4 of DE 102 09 025 discloses a ring which is displaceable axially outside a drum opening but cannot close the opening. That is because its external circumference is so much greater than the external circumference of the drum in this region that a gap always remains between the drum and ring. By contrast, according to the present disclosure, the ring completely closes the outlet openings, since the internal diameter of the circumferentially continuous ring and the external diameter of the drum are correspondingly matched to one another.
The actuating device may be designed as a fluidic, or hydraulic, actuating device. An actuating device of this type is of compact construction, is particularly operationally reliable and also relatively easy to implement on the rotating drum.
According to an embodiment of the present disclosure, such embodiment being simple to implement and inexpensive, the outlet openings are formed as apertures, such as drilled holes or slots, in the lateral surface of the drum. The embodiment including the slots is adapted for effective discharging of even a solids phase, since the slots may have a relatively large cross section. The slots may extend in the circumferential direction.
According to another embodiment of the present disclosure, the outlet openings are arranged axially before the continuously acting liquid discharge, which is effected, for example, by a scraper disk or by further openings in the drum lid.
It is advantageous if the outlet openings are formed in the lateral surface of the drum in such a manner that they lie radially outside a separation and/or clarification disk set made up of disks, with the clarification disk set connected upstream of the continuous liquid discharge. Disk sets in decanters are known for example from DE 100 65 060 A1.
Particularly in this upstream region, the additional outlet openings are particularly useful, since they can be used not only to drain out a residual liquid level but also for partial emptying, for example, a partial volume of 10 liters (1) during production or processing at full speed.
Alternatively, according to the present disclosure, it is possible to arrange the outlet openings in the drum lid.
In such an alternative, in particular in operation with the drum still rotating at high speed, it is possible to discharge flowable solids or product which has accumulated on the inner circumference of the drum lateral surface in this axial region of the drum.
Self-emptying drum separators of a different generic type are known, for example, from DE 38 21 486 A1 or DE 38 29 158 A1, which have ring slides for closing solids discharge openings. By contrast, in a decanter or centrifuge, according to the present disclosure, additional discharge openings are provided, which do not replace but rather complement the continuous solids discharge openings at the conical end of the drum, in order to simplify residual emptying of the drum.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.